1. Field of the Invention
This invention relates to power circuit control apparatus for primary and auxiliary loads of consumer electronics products and, more particularly, to power circuit control apparatus for energizing both loads when connected to a source of a-c potential and only the primary load when connected to a source of d-c potential.
2. Description of the Prior Art
In consumer electronics products such as portable radios and combination radio/tape recorders, it is common to provide means for permitting the product to be powered optionally by either a-c electric power from the house wiring or d-c electric power from a battery. Such consumer electronics products typically include a primary load consisting of the load elements which must be energized for product operation, such as radio receiver circuits, speaker drive circuits, and tape drive circuits. In addition, many such products include an auxiliary load consisting of one or more load elements not essential to product operation. Such load elements might include level meters and various lighting circuits for providing radio dial illumination, power on indication, and level meter illumination. In a full featured audio electronics product, the electric current required to drive the various load elements of the auxiliary load may be substantially greater than that required to drive the essential element of the primary load. In such a case, operation in the battery mode may not be entirely satisfactory due to excessive current demands, resulting in severely curtailed battery life and unacceptable operating cost.
One solution to this problem is to provide switching apparatus for connecting both the primary load and the auxiliary load to an a-c source and for connecting only the primary load to a d-c source. In this manner, all of the advantages provided by the auxiliary load elements can be enjoyed when essentially unlimited a-c electric power is available while providing reasonable life and economy when operating on battery power. In the prior art, such switching can be conveniently provided by means of multiple pole switches. Unfortunately, the initial cost of such switches tends to be relatively high, and they require extensive and expensive wiring during the manufacturing process.